Northern Prairie Wildlife Research Center
Canvasback 63.7 X 44.6 mm Redhead 60.2 X 43.4 mm Mallard 57.8 X 41.6 mm Scaup 57.0 X 39.4 mm Gadwall 55.3 X 39.7 mm American wigeon 53.9 X 38.3 mm Northern pintail 53.6 X 38.2 mm Northern shoveler 52.2 X 37.0 mm Blue-winged teal 47.1 X 33.9 mm Green-winged teal 45.8 X 34.2 mm
Evidence at nests should only be used to verify species identification when nests are found by methods that flush the hens. Species identification from evidence at nests is necessary in studies that include nests found after the eggs hatched or were destroyed or abandoned.
Certain characteristics are specific to the down and breast feathers and the eggs of each species, but considerable individual variation occurs, especially among breast feathers. By looking at several feathers in each nest it is often possible to find "key" breast feathers that permit positive species identification. However, key feathers may be absent or the presence of other body feathers may cause confusion. A reference sample of breast feathers and down taken from correctly identified nests can be very useful. Feathers should be collected from several nests of each species to depict the wide range of intraspecific variation.
Key points to note in breast feathers include relative size, coloration, and patterns between dark and light tones (Fig. A-1). The same principles apply to the down. Breast feathers can be identified more reliably than down but the size and color of down feathers or eggs often provide additional evidence.
Descriptions of the breast feathers, down, and eggs of ground-nesting ducks commonly found in the prairie pothole region follow. Species that might easily be confused are grouped together. Generally, dabbling ducks and lesser scaup are the primary upland nesters, but redheads and canvasbacks (Aythya valisineria) occasionally nest in upland cover.
Breast feathers of mallards are relatively larger than those of other ducks described. The central area is brown and extends in a broad pattern to the tip of the feather. Usually a suggestion of a cross or mottling is noted in the feather pattern. Distal margins are distinctly cinnamon colored. The northern shoveler also regularly has definite cinnamon coloration on the breast feathers, but the brown central area ("spot") does not extend to the tip. Mallard breast feather patterns vary considerably. Down feathers are light brown with a white center and little or no frosting on the tips. Eggs are larger than those of other dabbling ducks described and are usually pale olive buff or various shades of brown.
A typical breast feather pattern has a dark brown base extending in a narrow, well-defined strip to the distal tip of the feather. The lateral margins of this brown strip are light tan. This pattern is similar on mallard feathers, except that the margins are cinnamon colored on mallard feathers. Northern pintails and mallards are the two dabbling ducks that have a brown central stripe extending to the tip of the breast feather. Down feathers are brown and small in relation to the size of the hen. Egg color varies from greenish yellow to gray green.
Many observers believe this is the easiest species to identify from breast feathers. The feather has a large brown spot, almost in the center, surrounded by a light tan or cinnamon margin. Down feathers are brown with a relatively small white area in the center. The eggs are buff with a greenish tinge and are slightly larger than teal eggs but smaller than those of the northern pintail, gadwall, and American wigeon.
Characteristic breast feathers of gadwalls and American wigeons have two colors-light brown and tan or whitish tan. It is not uncommon, however, to find feathers that are all white or light tan with little tonal variation. When present, the central light brown does not extend to the tip. Several characteristics distinguish the two species: (1) the shape of the feather tends to be more oval for the gadwall and more rectangular for the wigeon, (2} the light-colored tip is proportionally wider on wigeon feathers, and (3) the demarcation between the light-colored feather tip and the darker basal area is curved on gadwall feathers but tends to be straighter on wigeon feathers. Broley (1950} described the demarcation line on breast feathers as curved for both species, but our observations have indicated otherwise.
Gadwall down feathers are dark with moderately white frosting on the tips. Wigeon down feathers are very dark, often nearly black, with conspicuously frosted tips. The relatively large eggs of gadwalls and wigeons are creamy white to pale olive buff.
The coloration and pattern of breast feathers vary. Some feathers have brown centers extending toward the base and contrasting light tan tips and edges. Other variations include feathers that tend to be light tan with several brown spots. Eggs are a creamy tan with very little variation among nests.
The down and breast feathers are very small. Breast feathers tend to have brown centers with light tan edges but are more rectangular than those of blue-winged teal. Nest bowls are smaller than those of the other species described. Green-winged teal eggs appear slightly smaller than blue-winged teal eggs and are creamy white to olive buff.
This species has very dark brown rectangular breast feathers with tan tips. Down feathers are black with very small white centers. Lesser scaup eggs are dark olive buff and are about the same size as mallard eggs, but are smaller than the eggs of redheads or canvasbacks.
Breast feathers are brownish gray with a white distal edge. Redhead nests can easily be identified by the pure white down. Redheads usually nest over water, but upland nests may be found.
Breast feathers are light grayish brown with a tan edge. Canvasback and redhead breast feathers are similar, but canvasback down is gray. Although canvasbacks almost always nest over water, nests have been found in upland cover. Eggs of canvasbacks and redheads are large and vary from buff to grayish white.
The following key was adapted from Broley (1950). The number of species was reduced from 24 in the original key to 8 that commonly nest in upland habitats in the prairie pothole region, plus the redhead and canvasback that occasionally nest in upland cover.